In recent years rigid containers have been replaced by flexible plastic pouches as liquid containers in a number of fields. Among the liquids which can be packaged in such pouches are wine, blood, intravenous fluids, and enteral nutrition solutions.
With the switch to this new container material, some problems have been solved but others have been created. One of the most common liquid container materials, glass, is of course brittle and therefore subject to shattering upon sudden impact. Less brittle materials, such as metals and rigid or semirigid plastics, are less subject to shattering, but are often dented by impact. Flexible pouches, on tne other hand, yield upon impact and thus resist both shattering and denting.
But one of the advantages of rigid and semi-rigid materials is that they absorb much of the shock of impact; whereas flexible materials yield so readily that they permit most of the shock to be transmitted to the liquid contents. In at least some applications that is a serious practical problem for the package designer.
In the case of some liquid products, such as medical nutritionals or infusion fluids which are packaged in flexible pouches, each pouch is formed of two sheets of plastic material placed in overlying relationship and secured together along their edges by heat-sealing or the like. At one end of the pouch is a port which is designed to be punctured by a needle or other sharp implement, in order to gain access to the liquid inside. In addition, adjacent to that port there may be a second port designed to be punctured by a similar instrument in order to permit air to enter the pouch as the liquid is withdrawn through the first port.
The port area (i.e., the ports and their surrounding heat seals) is the most fragile part of such pouches. In the event of a sudden impact, the port area is most vulnerable to the resulting shock waves transmitted by the liquid medium contained in the pouch. Because of this fact, the port area is subject to damage even as a result of an impact imparted at a considerable distance from the port end thereof.
The seriousness of the problem is demonstrated by a recent study which showed that the safe free-fall distance of such pouches, when packaged in paperboard cartons, is only fifteen inches. Thus, an ordinary corrugated shipping carton does not provide adequate protection for shipment through normal distribution channels.